Hello Venkat
I doubt whether your aggregates are getting filled in the first place. The aggregates screen is blank which should not be the case.
Use the debug + execute functionality from RSRT by checking Display aggregate found. By doing this it will let you know whether any aggregates are getting used when you run the query.
Refer this note to get into more information on query performance 1681396 - Query Performance
Regards
Gajesh
